Fuel cells have been proposed as a power source for electric vehicles and other applications. In proton exchange membrane (PEM) type fuel cells, hydrogen is supplied as a fuel to an anode of the fuel cell and oxygen is supplied as an oxidant to a cathode of the fuel cell. A plurality of fuel cells is stacked together in a fuel cell stack to form a fuel cell system. The fuel and oxidant are typically stored in pressurized hollow vessels such as fuel tanks, for example, disposed on an undercarriage of the vehicle.
The pressurized vessels may be multi-layered and include at least an inner shell and an outer shell. The inner shell may be formed from a plurality of components welded together. By using a welding process, the types of materials used to form the inner shell are restricted, and permeation of a stored fluid through weldseams of the welded inner shell may result.
Some inner shells are manufactured using a rotational molding method. Typically, the cycle time to prepare an inner shell using the rotational molding method is not optimal. The inner shell is formed utilizing the rotational molding method by disposing penetrating elements in a die cavity with a polymer resin, heating the mold while being rotated to cause the resin to melt and coat walls of the die cavity, cooling the die, and removing the molded inner shell. To form the outer shell, the molded inner shell may undergo a filament winding and curing process.
During the rotational molding, the penetrating elements may not properly adhere to the inner shell resulting in space therebetween. If the penetrating elements are not properly adhered to the inner shell, a fluid tight connection between the penetrating elements and the inner shell may not form. Without a fluid tight connection, the contents of the vessel may escape therefrom to the atmosphere. To ensure fluid tight connections between the penetrating elements and the inner shell, adhesives may be employed. However, insufficient amounts of adhesive and expansion and contraction of the vessel during use may also result in space between the penetrating elements and inner vessel. Heat welding of the penetrating elements and the inner shell, and other similar processes, may be used to form a fluid connection between the inner shell and the penetrating elements. Such welding processes may be time consuming and require non-automatable process steps, thereby resulting in an increased cost to produce the vessel. Heat welding processes are disclosed in U.S. Pat. No. 5,429,845 for BOSS FOR A FILAMENT WOUND PRESSURE VESSEL to Newhouse et al. Alternatively, an adapter device as disclosed in U.S. Pat. No. 7,032,767, hereby incorporated herein by reference in its entirety, may also be used to ensure a fluid-tight seal.
It would be desirable to develop a hollow pressure vessel and efficient method of forming the same having a penetrating element, an inner shell, an outer shell, and an interfacial layer formed on the penetrating element, wherein the interfacial layer facilitates a fluid tight attachment of the penetrating element to the inner shell.